NA-BA AND K-BA PARTITIONING BETWEEN FELDSPAR AND AQUEOUS CHLORIDE SOLUTIONS - SOME CONSEQUENCES OF UNMIXING IN SOLIDS AND FLUIDS

Experiments have been carried out at 600 and 750-degrees-C, 1.5 to 2.5 kbar, to determine the partitioning of Na and Ba or K and Ba ions bet ween feldspars and aqueous chloride solutions. At these temperatures ( Na,Ba)-feldspar unmixes near the sodic end-member and thus the solid s olution is very far from ideality. On the other hand, the (K,Ba)-felds par series deviates only slightly from ideality. The (Na,Ba) and (K,Ba ) chloride solutions show a large domain of unmixing and their critica l curves lie at higher pressure than for the other binary chloride sol utions previously studied, i.e. 2 kbar at 600-degrees-C and 2.4 kbar a t 750-degrees-C.